WIth FOB - you can leave engine running and either lock with fob, or with button on door handle.
Or shutdown and restart with remote start (which locks the doors and starts).
Shutdown/remote-start is probably the SAFER of the two options - as the truck can't be "fully started" and driven off without the fob present in the cabin. So that would prevent a "break-in/drive-off" incident (though any potential thief wouldn't know the difference and still break in, only to find they can't drive off - at which point I SHOOT THEM). Keeping in mind - if a thief drives off with a truck left running, they don't get a restart. "Thieves of opportunity" (the kind that jump into running vehicles) aren't vehicle security experts (RFID scanners and the like). And the experts don't need a fob to steal your truck if they really want it.
I haven't smoked in my truck ONCE in the 10 months since purchase (which people who know me find miraculous - and friends who smoke find ANNOYING) - so I frequently stop while out and about to grab a smoke. Here in SoFla I leave it running with AC full blast so I don't have to cool it off all over again. I do it both ways - depending on how far away from the truck I have to wander to find shade (or use the can).
As long as we're talking security - a few other things to suggest. Like - 1) DON'T PROGRAM YOUR HOME ADDRESS INTO THE FACTORY GPS - and - 2) DON'T PROGRAM THE GARAGE DOOR OPENER.
Obviously - both 1 & 2 to a "pro car thief" also gives them unrestricted access to YOUR HOME. I haven't checked it on the RAM - but my previous Honda Pilots, the in-car garage door openers worked even without the vehicle being on - so someone could easily break into the car and activate your door opener. Or steal your car, be lead right to your home and be in pretty damn fast. I keep a small opener fob on my keychain and it's just as easy to reach over and press the button, as it is to reach up to the visor (plus, my truck doesn't fit in my garage anyways).
I (personally) think the factory GPS sucks anyways - and use Google Maps (satellite view) and Music in iPhone Carplay Dual Screen mode anyways. Considering the base OS for the factory unit is likely a form of android (as most are) - wouldn't it be easier for car manufacturers to just use GOOGLE MAPS as their native GPS? No updates needed, much better GUI, better voice activated searches. I know - OFF TOPIC...
Rick